Process for the purification of titanium tetrachloride from traces of carbon compounds

ABSTRACT

This application discloses a process for purifying titanium tetrachloride from the carbon residues resulting from the purification of TiCl4 by means of organic compounds, the raw titanium tetrachloride being treated with aluminum trichloride at temperatures ranging between 100* C. and boiling temperature, and in the presence of from 0.01 to 1 percent (by weight of the TiCl4) of finely divided Ti02 having a particle size ranging between 0.05 and 10 microns.

United States Patent Inventors Fabrizio Guicciardi;

Paolo Palagi, both of Novara, Italy Appl. No. 820,663 Filed Apr. 30, 1969 Patented Oct. 26, 1971 Assignee Montecatini Edison S.p.A.

Milan, Italy Priority May 3, 1968 Italy l6033A/68 PROCESS FOR THE PURIFICATION OF TITANIUM TETRACHLORIDE FROM TRACES OF CARBON COMPOUNDS 3 Claims, No Drawings U.S. Cl 23/87 TP, 23/87 T, 23/202 V Int. Cl C0lg 23/02 Field of Search 23/87 TP, 87 T, 202 V References Cited UNITED STATES PATENTS 2,207,597 7/1940 Pechukas 23/87 X 2,344,319 3/1944 Meister 23/87 X 2,915,364 12/1959 Clabaugh et a1. 23/87 3,328,126 6/1967 Di Stefano et al. 23/202 3,350,171 10/1967 Callow et a1. 23/202 FOREIGN PATENTS 1,457,538 11/1966 France 23/87 Primary Examiner- Edward Stern Attorney-Stevens, Davis, Miller & Mosher ABSTRACT: This application discloses a process for purifying titanium tetrachloride from the carbon residues resulting from the purification of TiCl, by means of organic compounds, the raw titanium tetrachloride being treated with aluminum trichloride at temperatures ranging between 100 C. and boiling temperature, and in the presence offrom 0.01 to 1 percent (by weight of the TiCl of finely divided T10 having a particle size ranging between 0.05 and 10 microns.

PROCESS FOR THE PURIFICATION OF TITANIUM TETRACHLORIDE FROM TRACES OF CARBON COMPOUNDS of purity in order to yield a Ti product with satisfactory pig- 0 mentary characteristics.

While some of the substances present in the raw TiCl, as impurities may be separated in a practically quantitative way by physical methods, this is not the case with the vanadium compounds present, for which it is necessary to resort to chemical l methods of separation.

One of the methods most frequently in use at the present time consists in treating the raw TiCl with organic compounds, preferably mineral or vegetable oils, which change the vanadium salts into nonvolatile compounds US. Pat. Nos. 2,230,538, 2,592,021, 2,824,050 and 3,156,630).

This method has, however, the disadvantage of leaving in the purified TiCl, traces of carbon compounds which exert a harmful action on the subsequent process of combustion to Ti0,.

These carbon compounds normally are separated from the TiCl, in the form of flakes, by the addition of small amounts of AICI; to the hot TiCh, preferably at the boiling point of TiCl (136.4" C.) (French Pat. No. 1,457,538). This method, however, is not satisfactory for several reasons.

In fact, on the basis of our experimental tests, we have found that at the boiling temperature of the TiCl the addition of increasing amounts of A1Cl;,, varying from 0.5 to 2.5 percent by weight of TiCl does not cause a parallel drop of the settling time which remains in general greater than 25 minutes. The treatment with AlCl at temperatures below the boiling point, up to 100 C. involves very high settling times or the use of too high percentages of AlC1 Furthermore, it has been found that the values of the settling times obtained by repeated tests vary widely. This phenomenon must be attributed to the light flaky nature of the product separated, following the action of the Alcl In fact, the convection motions which are generated inside the liquid mass of TiCl, by the effect of thermal gradients prevent the settling of the impurities, or else bring these back into suspension once they have settled, thus preventing the formation of a clear solution suitable for subsequent use.

The object of this invention is to provide a process for the purification of TiCl, from carbon compounds, which shall not show any of the disadvantages of the methods of the abovecited prior art.

More particularly, an object of this invention is that of providing a process for the purification of TiCl, from carbon compounds through the addition of aluminum chloride by means of which are obtained, with very short settling times, deposits of impurities of such a compactness and density as to prevent their redispersion and to allow an easy decantation of the clear supernatant TiCL.

These and still further objects are attained by means of this invention, according to which it has been found that the presence in the mixture of TiCl and AlCl; of small quantities of finely divided H0 in quantities varying from 0.01 to 1 percent, but preferably from 0.1 to 0.5 percent by weight of the C1,, not only reduces the settling time, but also generates a compact and dense deposit, which does not disperse again easily. The particle size of the Ti0, used for the purpose varies from 0.05 to 1 micron, although also greater particle sizes, such as from 5 to microns or particle aggregates still yield good results.

Ti0, is preferred for this use because it avoids contamination of the treated TiCL to be used in the successive combustion step. However, other inorganic substances inert towards TiCh, and of high specific surface (in particular metal oxides such as Si0,, A1 0 Zr0,, etc. may also be used and will produce equally satisfactory results.

The treatment of the TiCh with AICI, in the presence of Ti0, is carried out with vigorous stirring, at temperatures between 100 C. and the boiling point of TiCl preferably at the latter temperature, with stirring periods of from to 15 minutes.

Once the predetermined time interval has elapsed, the stirring and heating are discontinued, allowing the temperature to drop below the boiling point, for instance to 90 C. The precipitate is thus to settle and the clear TiCL is then separated.

The following detailed working example is given merely still further to illustrate the invention:

EXAMPLE The testing apparatus consists of a graduated pyrex cylinder with a conical bottom, provided with an efficient stirring system, a thermometer and a condenser, immersed in a thermostatic bath.

lnto 860 g. of TiCL of commercial quality, which had been treated with oleic acid for separating the V compounds, and still containing 0.02 percent (expressed as C) of carbon compounds, are introduced varying amounts of Tit), (see the table) with a particle size ranging between 0.1 and 0.5 micron and heated in the cylinder up to the boiling point. Thereupon are added 4.3 g. of MCI, in an inert atmosphere while the mixture is kept at the boiling temperature for one hour with vigorous stirring.

The stirring is then discontinued and the temperature of the system reduced to 90 C. The values of the settling times ob tained in the presence of the Ti0, are well reproducible, while as clearly appears from the following table-in the absence of Ti0 these values vary widely.

l. A process for purifying titanium tetrachloride from the carbon residues resulting from the purification of the titanium tetrachloride by means of organic compounds, which comprises the steps of:

a. admixing the raw titanium tetrachloride with aluminum chloride, wherein the aluminum chloride is from 0.5-2.5 percent by weight of the titanium tetrachloride;

b. subjecting the mixture to (l) vigorous stirring in an inert atmosphere, and (2) at a temperature from between C. and the boiling point of the titanium tetrachloride, and (3) for 15 to 90 minutes and (4) in the presence of from 0.1-i percent, based on the weight of the titanium tetrachloride, of finely divided Ti0 with a particle size of from 0.05 to 10 microns:

c. cooling the resultant mixture;

d. separating the compact and dense precipitate of the carbon residues, which has a settling time of from about 1 to about 3 minutes, from the purified titanium tetrachloride.

2. A process according to claim 1, wherein the Ti0 is used in amounts ranging from 0.1 to 0.5 percent by weight with respect to the TiC1,.

3. A process according to claim 1 wherein the Ti0 is used in particle sizes between 0.05 and 1 micron. 

2. A process according to claim 1, wherein the Ti02 is used in amounts ranging from 0.1 to 0.5 percent by weight with respect to the TiCl4.
 3. A process according to claim 1 wherein the Ti02 is used in particle sizes between 0.05 and 1 micron. 